Tower defence where you torture your enemies

Greetings, I'm working on a tower defence where you play as a Mage hunted by the Holy Knights.

The game play loop is your normal Tower defence games with one twist; Instead of making money by simply killing the enemies you must torture them in your dungeon, What else a good mage would do. This idea was inspired by game called Dungeon keeper it was pretty funny to torture people in there. Unfortunately I had no time expanding this game mechanic, turned out making TD is not as simple as I thought, But I am working on it. Currently There is a few devices to torture and cages to expand amount of prisoners you may have, all enemies shell give same amount of souls(money) and shell die after fixed amount of torture cycles. Since game is all about torturing people I am willing to expand on this ide without over complicating game-play. Few ideas I have in mind. different enemies shell give different reward, have a different durability. I was thinking to add different type of cages for different enemies but I thought I'll make game to complicated and add too much macro.

Any way that's I had to share. If you have any thing to say pleas do so. 

Have a nice day.